Since a large amount of scum gathers on a water surface in a starting or final settling pool, it is necessary to remove the scum efficiently. In order to remove the scum, the applicant has suggested the following scum removal apparatus.
FIGS. 26 and 27 illustrate the scum removal apparatus S the applicant has previously suggested. In a rectangular settling pool provided with this scum removal apparatus, there is provided a plurality of (for example, four) sprocket shafts 200 having their longitudinal axes oriented across the width of the pool, a pair of sprocket wheels 201 mounted on each of the sprocket shafts 200, and left-hand and right-hand endless chains trained around the respective sprocket wheels 201 of each pair.
The scum removal apparatus is so designed as to be driven by the utilization of some or all of flights 203 secured to the endless chains 202 for drawing and removing the scum (floating matter).
The scum removal apparatus is provided with a trough 205, a guide support sheet 206, a weir 208 and a transmission mechanism 209. The trough 205 is of a generally U-shaped cross-section, top side and a front side of which are opened, and is fixed in position within the pool with its longitudinal direction oriented across the width of the pool.
The guide support sheet 206 is in the form of a generally elongated band of a length corresponding to the length of the trough 205 and is made of rubber material. This guide support sheet 206 is secured to the front side of the trough 205 so as to protrude outwardly therefrom and is capable of bending up and down by the effect of its elastic deformation. The weir 208 is of a generally triangular-sectioned hollow body which may often have a foaming material filled therein. This weir 208 is secured to a front side of the elastically deformable guide support sheet 206 so as to protrude outwardly therefrom and is capable of moving up and down on respective sides of a water surface 207 while being supported by the sheet 206.
The up and down movement of the weir 208 is effected by an actuating mechanism 209.
The actuating mechanism 209 comprises a rotary shaft 210 and a drive arm 211. The rotary shaft 210 extends over the width of the pool while the drive arm 211 is a single arm extending from one end of the rotary shaft 210 in a direction perpendicular thereto. A free end of the drive arm 211 is provided with a cam plate 213 having a cam surface defined at bottom thereof. The cam surface has two cam projections 213a and 213c and a recess 213b delimited between the cam projections 213a and 213c, all defined on the cam surface. Rollers 214 protruding from one end of the flights 203 (movable members) are used to move the cam plate 213 to drive the drive arm 211 and an operating arm 212 so that the weir 208 can be driven up and down through a rod 224 and an operatively associated arm 225. Each of the rollers 214 is secured to a bracket connected to one end of each flight 203 adjacent the earn plate 213.
The operating arm 212 cooperates with the rod 224 and the operatively associated arm 225 to form the transmission mechanism and extends in a direction towards the trough 205, which is counter to the direction of extension of the drive arm 211. This operating arm 212 is employed on each of the left-hand and right-hand sides of the pool.
The above described scum removal apparatus operates in the following manner.
When a motor not shown but installed outside adjacent to the pool is powered, the chains 202 are driven in a direction indicated by an arrow, accompanied by a low-speed circulatory movement of the flights 203 which are disposed on an outer circumference of the chains 202 in a circumferentially equally spaced relationship with each other. These flights 203 serve to drag sediments setting at the bottom of the pool and guide them towards a pit, and the sediments so guided to the pit are discharged out of the pool by a pump not shown. As some of the flight 203 travel upwardly and adjacent the water surface, the associated rollers 214 mounted each end of those flights 203 are successively brought into engagement with the cam plate 213 to shift the latter upwardly.
The rollers 214 are successively brought into contact with the projection 213a, then the recess 213b and finally the projection 213c, causing the cam plate 213 to move up and down. Specifically, when each roller 214 is brought into engagement with the first-stage projection 213a, both of the cam plate 213 and the drive arm 211 are lifted a considerable distance while the operating arm 212 is correspondingly lowered, causing the welt 208 to be lowered below the water surface through the rod 224 and the operatively associated arm 225. At this time, scum floating on the water surface, whichever small or large in size, are guided by the action of a flooding motion of water into the trough 205 and is then discharged out of the trough 205.
When the roller 214 is then brought into engagement in the recess 213b, both of the cam plate 213 and the drive arm 211 are temporarily lowered while the operating arm 212 is lifted, causing the weir 208 to be shifted upwardly a slight distance with its upper edge brought immediately to a level below the water surface and, accordingly, the amount of water being flooded over the weir 208 is correspondingly reduced. Although the amount of water is reduced, the velocity of flow of water increases conversely and, accordingly, a force necessary to draw the scum acts to a point on the water surface further away from the weir 208 and the scum even at the point further away from the weir 208 is therefore drawn smoothly towards the trough 205.
However, when the roller 214 is finally brought into engagement with the second-stage projection 213c, the drive arm 211 carrying the cam plate 213 is gain lifted while the operating arm 212 is lowered, and therefore, the weir 208 is lowered with the consequence that a large amount of scum having been drawn close to the weir 208 is guided into the trough 205. In this way, since the cam plate 213 is of a generally ladder-like configuration, the draw of the scum towards the weir 208 and the subsequent overthrow of the scum into the trough 205 are performed effectively.
The scum removal apparatus S is installed one at each pool and, while the trough 205 in one scum removal apparatus S is installed so as to incline in one direction, the troughs 205 of all scum removal apparatuses S are fluid-connected with each other by means of connecting troughs. The scum and water having flown into one of the troughs 205 which is positioned at the highest level with respect to the direction of downward inclination flow by gravity to the final trough 205 at the lowest level through the intermediate trough or troughs 205 via the associated connecting trough or troughs. The scum and the water having flown into the illustrated intermediate trough 205 then flows into the next succeeding trough 205 through the corresponding connecting trough at the lower level with respect to the direction of downward inclination and are then discharged out of the treatment pool at the lowest level. It is to be noted that each connecting trough is fixed in position with its opposite ends communicated with respective holes formed in portions of walls of the neighboring pools.
Since the scum removal apparatus S is of a type wherein the up and down movement of the cam plate 213 is induced so that the up and down movement of the cam plate 213 can result in an up and down movement of the weir 208, the rotary shaft 210 is required to extend generally across the width of the pool and, since the weir 208 is supported elastically by the guide support sheet 206 made of rubber material, the number of the operating arms 212 extending between the rotary shaft 210 and the weir 208 is not one, but two. With this structure, the drive arm 211, the rotary shaft 210 and the operating arms 212 spread in a plane and, therefore, not only does it bring about an increased cost of manufacture, but also a large-scale construction work is required to make them extend from one end to the other of the pool, resulting in the construction at the site taking a large amount of man power and that of time.
Also, since the cam plate 213 is used to produce the up and down movement necessary to drive the drive arm 211 upwardly a considerable distance, there is a possibility that, if there is a ceiling above the pool, the cam plate 213 may contact the ceiling and, therefore, a manufacturer may find a difficulty in accommodating the request made by the user.
Accordingly, the present invention has been developed to provide a scum removal apparatus which is substantially free from the problems inherent in the conventional scum removal apparatus, which can be manufactured compact and at a reduced cost, and which can be easily installed.